CVE-2021-31808 is a medium-severity vulnerability affecting Squid versions prior to 4.15 and 5.x before 5.0.6. The vulnerability stems from an input-validation bug that exposes the application to a Denial of Service (DoS) attack. This allows an attacker to send a crafted HTTP Range request, which can disrupt service for all clients using the proxy. With a CVSS score of 6.5, organizations must recognize the potential impact of this flaw.
The urgency for defenders is moderate; however, given the potential for service disruption, organizations should address this vulnerability in their priority patch cycle. The nature of the attack vector being network-based and low complexity implies that it can be exploited with minimal effort from an attacker.
As of now, there is no known public exploit for CVE-2021-31808, and it has not been included in the Known Exploited Vulnerabilities (KEV) catalog. However, due diligence in monitoring and patching is essential to mitigate risks associated with potential exploitation.
Organizations are advised to assess their environments for the affected versions of Squid and implement the necessary patches to remediate this vulnerability. Given the high impact on availability, prioritizing patching is crucial.
Vulnerability Details
An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Due to an input-validation bug, it is vulnerable to a Denial of Service attack (against all clients using the proxy). A client sends an HTTP Range request to trigger this.
This vulnerability falls under the CWE-190 classification, indicating arithmetic issues related to input validation.
The vulnerability has a CVSS score of 6.5, categorized as medium severity. The score signifies that this vulnerability can lead to high availability impact (denial of service), while confidentiality and integrity impacts are rated as none.
Technical Analysis
The root cause of CVE-2021-31808 is an input-validation flaw in Squid's handling of HTTP Range requests. When such requests are improperly validated, it allows for manipulation that can exhaust server resources, leading to service unavailability.
This vulnerability can be exploited over the network, requiring low privileges for the attacker. There is no user interaction needed to trigger the attack, making it particularly dangerous.
The availability impact is categorized as high because successful exploitation can result in total service disruption for all clients using the proxy service.
Risk & Impact Analysis
Risk to organizations includes potential service disruption, affecting user access and business operations. The impact of a Denial of Service attack can result in significant downtime, which may lead to loss of revenue and customer trust.
Given the moderate urgency associated with this vulnerability, organizations should prioritize it within their patch management strategy. The potential blast radius is considerable, especially for organizations heavily reliant on Squid for proxy services.
As this vulnerability is not actively exploited in the wild, organizations still must remain vigilant and proactive in applying updates and monitoring their systems for any signs of compromise.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
Squid versions before 4.15 and those in the 5.x series before 5.0.6 are affected by this vulnerability. Organizations using these versions should prioritize patching to mitigate potential risks.
Mitigation & Remediation
To remediate CVE-2021-31808, organizations should update to Squid version 4.15 or 5.0.6 and later. If immediate patching is not feasible, administrators should consider implementing network controls to restrict access to the proxy service as a temporary measure.
Moreover, organizations can benefit from conducting regular security assessments and audits to identify similar vulnerabilities proactively. Engaging in application security assessments is recommended to ensure comprehensive security posture.
Detection Guidance
Monitoring logs for unusual HTTP requests, particularly those containing Range headers, can help detect potential exploitation attempts. Additionally, organizations should watch for behavioral anomalies in network traffic that may indicate an ongoing attack.
AppSecure Threat Intelligence Insight
CVE-2021-31808 highlights the importance of input validation in web applications. Security teams should ensure thorough validation processes are integrated into their development lifecycle to prevent similar vulnerabilities.
This vulnerability serves as a reminder of the evolving landscape of web security threats. Organizations can benefit from adopting a penetration testing methodology to identify and remediate weaknesses before they can be exploited.
To fortify defenses, organizations should integrate security awareness training for developers, focusing on secure coding practices that mitigate the risk of vulnerabilities like CVE-2021-31808.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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